Lithography projection objective, and a method for correcting image defects of the same

ABSTRACT

Projection objectives, as well as related components, systems and methods, are disclosed. In general, a projection objective is configured to image radiation from an object plane to an image plane. A projection objective can include a plurality of optical elements along the optical axis. The plurality of optical elements can include a group of optical elements and a last optical element which is closest to the image plane, and a positioning device configured to move the last optical element relative to the image plane. Typically, a projection objective is configured to be used in a microlithography projection exposure machine.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 12/265,090, filed on Nov. 5, 2008, which is a continuation ofU.S. patent application Ser. No. 11/955,662 filed on Dec. 13, 2007,which application was a continuation of International Patent applicationPCT/EP2006/005059 filed on May 26, 2006, which designates the UnitedStates and which claims priority of U.S. provisional application No.60/690,544, filed Jun. 14, 2005.

BACKGROUND OF THE INVENTION

The invention relates to a lithography projection objective for imaginga pattern arranged in an object plane of the projection objective onto asubstrate to be arranged in an image plane of the projection objective.

The invention further relates to a method for correcting image defectsin the case of a lithography projection objective that can be tuned toimmersion operation.

A projection objective of the type mentioned at the beginning ispreferably used for microlithography projection exposure machines forproducing semiconductor components and other finely structuredsubassemblies. A projection objective serves the purpose of projectingpatterns from photomasks or graticules, which are also designated asmasks or reticles, onto an object, that is to say a substrate, coatedwith a photosensitive layer, or onto a semiconductor wafer coated withphotoresist, with very high resolution.

The resolution of the imaging of the pattern by the projection objectiveis proportional to the wavelength of the light used, and inverselyproportional to the image-side numerical aperture of the projectionobjective. The resolution can therefore be improved with the aid ofshorter wavelengths and higher numerical apertures. The numericalaperture NA is given by NA=n·sin Θ, n being the refractive index of themedium between the substrate and the last optical element of theprojection objective.

Hitherto, use has predominantly been made of projection objectives inthe case of which there exists in the image space between the exitsurface of the last optical element of the projection objective and theimage plane a finite working distance that is filled during operationwith air or another suitable gas. Such systems are designated as “drysystems” or “dry objectives”. The working distance between the lastoptical element and the substrate is generally filled in this case withhelium, nitrogen or another gas or a gas mixture with a refractive indexn of approximately 1.

It follows from the previously mentioned relationship between theresolution and the image-side numerical aperture that the resolution canbe raised when an immersion medium of high refractive index isintroduced into the working distance between the exit surface of thelast optical element and the substrate. This technique is designated asimmersion lithography. A projection objective of this type is alsodesignated as an “immersion system” or “immersion objective”. Somerefractive projection objectives that are suitable for immersionlithography and have image-side numerical apertures NA>1 are disclosedin the patent applications DE 102 10 899 and PCT/EP02/04846 of the sameapplicant.

A further advantage of an immersion objective consists in thepossibility of obtaining a larger depth of field of the imaging inconjunction with the same numerical aperture as for a dry objective.This advantage is used in the projection objectives according to theinvention.

In the case of an immersion objective, instead of being filled with agas, the space between the exit surface of the last optical element ofthe projection objective and the substrate, which determines the workingdistance, is filled with an immersion medium of a refractive indexsubstantially greater than 1. An immersion medium normally used atpresent is water, but it is possible, particularly within the scope ofthe present invention, to select other immersion media in accordancewith needs and suitability.

Document EP 1 431 826 A2, which stems from the same applicant, describeshow simple design means and manipulations can be used to tune aprojection objective between a dry operation (dry configuration) and animmersion operation (immersion configuration). The projection objectivedescribed there has a multiplicity of optical elements that are arrangedalong an optical axis of the projection objective, the optical elementscomprising a first group, following the object plane, of opticalelements and a last optical element that follows the first group, isnext to the image plane and defines an exit surface of the projectionobjective that is arranged at a working distance from the image plane.The last optical element is substantially free from refractive power andhas no sag or only a slight one. The tuning method described therecomprises varying the thickness of the last optical element, changingthe refractive index of the space between the exit surface of the lastoptical element and the substrate by introducing or removing animmersion medium, and moreover preferably an axial displacement of thelast optical element for the purpose of setting a suitable workingdistance in the dry operation of the projection objective. Moreover, itis provided to refine the tuning to the dry configuration or theimmersion configuration by changing the air spaces between individualoptical elements of the first group or by providing or varying aspheres.

The projection objective of the present invention can likewise be tunedbetween a dry configuration and an immersion configuration.

However, the present invention is based on a further aspect of such aprojection objective that can be tuned between the dry configuration andthe immersion configuration.

A temperature change usually occurs during operation of a projectionobjective. This can be global, homogenous or else local. For example,the air around the projection objective, the projection objectivehousing, the individual mounts of the optical elements, the opticalelements themselves and the air or the gas inside the projectionobjective and, during immersion operation, the immersion liquid can heatup.

It has emerged that temperature changes have a different effect withregard to spherical image defects on a projection objective duringimmersion operation than on a projection objective in the dryconfiguration. In other words, dry objectives and immersion objectivesdiffer from one another with regard to their sensitivity to temperaturechanges.

In the case of a projection objective in dry configuration, suchspherical aberrations induced by temperature changes can be at leastlargely compensated even in the relatively high order by simplyrefocusing in which only the position of the substrate is adjusted inthe direction of the optical axis. Specifically, a change in the workingdistance between the exit surface of the last optical element and thesubstrate leads in the case of a projection objective in dryconfiguration to very similar aberrations such as heating up of theprojection objective, and so the aberrations induced by the heating upcan be at least largely compensated by an appropriately directeddisplacement of the substrate, usually in conjunction with heating up,in a direction away from the last optical element.

It came out that this mode of procedure, specifically a correction ofimage defects on the basis of temperature changes solely by adjustingthe position of the substrate does not lead in the case of a projectionobjective in immersion configuration to the result as in the case of aprojection objective in dry configuration, that is to say in the case ofsuch a focusing correction in which the Zernike coefficient Z4 iscompensated to zero, higher spherical Zernike coefficients Z9, Z16, Z25,. . . remain and impair the imaging properties of the projectionobjective in immersion configuration.

SUMMARY OF THE INVENTION

It is the object of the invention to improve a projection objective thatcan be or is tuned to immersion operation with regard to its imagingproperties or with regard to the correctability of image defects thatare caused by a disturbance during immersion operation, such as a changein temperature, for example.

It is also the object of the invention to specify a method forcorrecting image defects of a projection objective that can be or istuned to immersion operation, which can be carried out with the aid ofsimple means.

According to the invention, a lithography projection objective accordingto claim 1 is provided for achieving the first mentioned object.

According to the invention, a method for correcting aberrations in thecase of a projection objective that can be, or is, tuned to immersionoperation is specified according to claim 29 for the purpose ofachieving the object mentioned in the second instance.

A lithography projection objective according to the invention forimaging a pattern to be arranged in an object plane of the projectionobjective onto a substrate to be arranged in an image plane of theprojection objective has a multiplicity of optical elements that arearranged along an optical axis of the projection objective. The opticalelements comprise a first group, following the object plane, of opticalelements, and a last optical element, which follows the first group andis next to the image plane and which defines an exit surface of theprojection objective and is arranged at a working distance from theimage plane. The projection objective can be or is tuned with respect toaberrations for the case that the volume between the last opticalelement and the image plane is filled by an immersion medium with arefractive index substantially greater than 1. The position of the lastoptical element can be adjusted in the direction of the optical axis. Apositioning device is provided that positions at least the last opticalelement during immersion operation such that aberrations induced by adisturbance caused by the operation of the projection objective are atleast partially compensated.

The method according to the invention for correcting image defects inthe case of a lithography projection objective that can be, or is, tunedto immersion operation comprises the step, in the event of a disturbancearising during immersion operation of the projection objective, ofpositioning at least the last optical element such that aberrationsinduced by the disturbance are at least partially compensated.

A disturbance in the case of the abovementioned projection objective orthe abovementioned method is, for example, a change in temperature. Thepresent invention is based on the finding that in the event of a changein temperature owing to heating up of the projection objective theworking distance between the exit surface of the last optical elementand the substrate is varied by the thermal expansion of the projectionobjective. However, since the immersion medium is located between thelast optical element and the substrate during immersion operation, thischange in the working distance leads to other sensitivities of theprojection objective during immersion operation than by comparison withdry operation. In dry operation of the projection objective, the changein working distance has no influence on the aberrations, while thechanged working distance, and thus the changed layer thickness of theimmersion liquid during immersion operation, induces additionalaberrations. These additional aberrations during immersion operationcannot be compensated solely by displacing the substrate in thedirection of the optical axis, as in the case of the dry objective.

An instance of “disturbance” in the meaning of the present invention canalso be one that is not caused by temperature, but is based, forexample, on bubble formation in the immersion liquid, unevenness of thewafer surface, a locally differing wafer thickness or other geometryerrors, and which renders refocusing necessary. This refocusing can beaccomplished by displacing the wafer stage and/or displacing opticalelements in the direction of the optical axis.

The inventive solution to this problem now consists, in the event of adisturbance, in positioning at least also the last optical element suchthat aberrations induced by the disturbance are at least partiallycompensated via the positioning of the last optical element. Inparticular, and preferably, by means of positioning of the last opticalelement the volume filled with the immersion medium, which can change inthe event of disturbance such as a thermal expansion, can be set bymeans of the positioning device such that the aberrations induced by thedisturbance, in particular aberrations of higher order, are at leastlargely compensated. By contrast with refocusing solely by adjusting theposition of the substrate in the direction of the optical axis in thecase of a projection objective during dry operation, now at least alsothe position of the last optical element is adjusted in the direction ofthe optical axis in order to keep the working distance, and thus thelayer thickness of the immersion medium, preferably at a nominal value,while the gas-filled or air-filled space between the last opticalelement and the penultimate optical element of the projection objectiveis kept variable.

It is preferably also possible to adjust the position of the substratein the direction of the optical axis, and the positioning device adjuststhe last optical element in a ratio correlated with the adjustment ofthe position of the substrate. In particular, the ratio between theadjustment of the position of the substrate and the adjustment of theposition of the last optical element can be selected to be 1:1.

With this type of “alternative focusing” in the immersion system bycomparison with focussing in the dry system, the same focussingsensitivities are achieved in the immersion objective as in the case offocusing in the dry objective, in which only the substrate is displacedwithout adjusting the position of the last optical element in thedirection of the optical axis.

Depending on requirement and degree of optimization, the ratio betweenthe adjustment of the position of the substrate and the adjustment ofthe position of the last optical element can also be selected to begreater than or less than 1:1.

For the purpose of further optimizing the imaging properties of theprojection objective during immersion operation, it is preferred in afirst step to adjust only the position of the last optical element inthe direction of the optical axis in order to restore a predetermineddesired working distance, and in a second step the position of the lastoptical element and the position of the substrate are adjusted in thedirection of the optical axis, preferably in the ratio of 1:1.

It is also possible here to interchange the first step and the secondstep in the sequence, or it can be provided to carry out these two stepsin an interlocking fashion.

It has emerged that optimum corrections of the imaging properties, inparticular even in higher orders of the spherical aberrations, thatcorrespond to the achievable corrections in the dry configuration can beachieved by controlling the working distance filled with immersionmedium to a nominal value that corresponds, for example, to the optimumvalue which is pre-calculated in the cold state of the projectionobjective, and the refocusing, as mentioned above, by simultaneouslyadjusting the position of the substrate and of the last optical elementin the ratio of preferably 1:1.

The working distance is preferably measured before and/or duringoperation of the projection objective, in order to enable permanentcontrol of the working distance. The respective measurement results arethen used to adjust the position of the last optical element and/or ofthe substrate.

The measuring device preferably cooperates with an actuator in order toregulate the working distance to a nominal value. This enablesunchanging optimum imaging properties of the projection objective duringoperation of the projection objective, that is to say the projectionobjective is capable of reacting to any sort of disturbance, for examplechanges in temperature, without manipulations from outside.

In a preferred alternative, it is also possible to proceed such that theposition of the last optical element is adjusted so that aberrations cansubsequently be at least largely compensated solely by adjusting theposition of the substrate.

In this mode of procedure, the temperature sensitivities of theprojection objective are therefore adapted during immersion operationsuch that, as in dry operation, they are again compatible with thesensitivities that exist from solely adjusting the substrate.

In the case of the projection objective, the last optical element ispreferably assigned at least one actuator for adjusting the position ofthe last optical element in the direction of the optical axis.

Alternatively or cumulatively, the positioning device can have a mountfor the last optical element that, upon heating up, moves the lastoptical element in a direction running counter to the thermal expansionof the projection objective.

This type of mounting technique for the last optical element with theuse of materials with various coefficients of thermal expansionadvantageously ensures that despite thermal expansion of the projectionobjective the working distance between the last optical element and thesubstrate can be kept at least approximately at the nominal value. Thisrenders it possible even without additional actuators to compensate theaberrations induced by disturbance, or these are already avoided fromthe beginning.

In accordance with further preferred measures specified in the claims,the projection objective according to the invention can be tuned betweendry operation and immersion operation.

Further advantages and features emerge from the following descriptionand the attached drawing.

It is self-evident that the abovementioned features which are still tobe explained below can be used not only in the combination respectivelyspecified, but also in other combinations or on their own withoutdeparting from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are illustrated in the drawingand explained in yet more detail here with reference thereto. In thedrawing:

FIG. 1 shows a schematic projection objective in immersionconfiguration;

FIG. 2 shows the projection objective in FIG. 1 in dry configuration;

FIG. 3 shows a bar diagram for illustrating the influence of adisplacement of the substrate in the direction of the optical axis on awavefront change in a comparison between the projection objective inFIG. 2 (dry configuration) and the projection objective in FIG. 1(immersion configuration);

FIG. 4 shows a bar diagram in which the fractions of higher sphericalaberrations (Z9, Z16, Z25, Z36) in relation to the Z4 fraction of thespherical aberration are illustrated by comparison with the projectionobjective in FIG. 2 and the projection objective in FIG. 1;

FIG. 5 shows a bar diagram that shows the temperature sensitivities ofthe projection objective in FIG. 2 in comparison with the temperaturesensitivities of the projection objective in FIG. 1;

FIG. 6 shows a bar diagram that illustrates the temperaturesensitivities of the projection objective in FIG. 2 in comparison withthose of the projection objective in FIG. 1 with and without correctionof the Z4 fraction of the spherical aberration to the value zero;

FIGS. 7 a) and b) show a detail of the projection objective in FIG. 1 intwo different states;

FIG. 8 shows a bar diagram similar to FIG. 6 although aberrations ofhigher order are illustrated after an identical displacement of the lastoptical element and the substrate for the projection objective in FIG. 1in accordance with FIG. 7 b) (the ratio between the adjustment of theposition of the substrate and the adjustment of the position of the lastoptical element being equal to 1:1);

FIG. 9 shows a bar diagram, comparable to the bar diagram in FIG. 8,after a further error correction of the projection objective in FIG. 1(the ratio between the adjustment of the position of the substrate andthe adjustment of the position of the last optical element not beingequal to 1:1);

FIG. 10 shows a schematic of a mount for the last optical element thatcompensates or overcompensates a temperature-induced change in theworking distance;

FIG. 11 shows an embodiment of a projection objective in immersionconfiguration, in which the present invention can be used; and

FIG. 12 shows a further embodiment of a projection objective inimmersion configuration in which the present invention can likewise beimplemented.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 illustrates a projection objective, provided with the generalreference numeral 10, in immersion configuration.

The projection objective 10 is used for the microlithographic productionof semiconductor components and other finely structured subassemblies.The projection objective operated with ultraviolet light from the deepUV region (for example 193 nm) serves to image onto a substrate 14,which is arranged in an image plane 15 of the projection objective 10, apattern 12 of a photomask (reticle) that is arranged in an object plane13 of the projection objective.

The projection objective 10 has a multiplicity of optical elements inthe form of lenses, but can also have both lenses and mirrors.

The optical elements are arranged along an optical axis 16 of theprojection objective 10.

The optical elements comprise a first group 18 of optical elements thatfollow the object plane 13 or the pattern 12. Three optical elements 18a, 18 b and 18 c of the first group 18 are illustrated by way of examplein FIG. 1.

The optical elements further comprise a last optical element 20 thatfollows the first group 18 and is closest to the substrate 14 or theimage plane 15.

The last optical element 20 is illustrated in FIG. 1 as a plane-parallelplate. However, the last optical element 20 can also respectively haveon the entrance side and exit side a radius of curvature that are,however, only so large that aspheric aberrations induced by thedisplacement of the optical element 20 in the direction of the opticalaxis 16 are sufficiently small.

Like the optical elements of the first group, the last optical element20 can be made from synthetic quartz glass. Furthermore, the lastoptical element 20 can also comprise a number of components in thedirection of the optical axis.

An exit surface 22, facing the image plane 15, of the last opticalelement 20 also simultaneously forms the exit surface of the projectionobjective 10.

A distance between the exit surface 22 of the last optical element 20and the surface of the substrate 14 defines a working distance 24.

The last optical element 20 is spaced sufficiently far away, forexample, by a few millimeters, from the first group 18 of opticalelements, such that the position of the last optical element 20 can beadequately adjusted in the direction of the optical axis 16.

The working distance 24 between the last optical element 20 and thesubstrate 14 is filled with an immersion medium 26. The immersion medium26 is, for example, an immersion liquid, for example water, that has arefractive index of n≈1.437 given an operating wavelength of λ=193 nm.

In the configuration illustrated in FIG. 1, the projection objective 10is designed for immersion operation, that is to say, with reference tothe aberrations produced, it is designed for, that is to say tuned to,the presence of the immersion medium 26 at the working distance 24.

FIG. 2 shows the projection objective 10 in FIG. 1 in its dryconfiguration. The transition of the projection objective 10 in FIG. 1(immersion configuration) to its dry configuration in FIG. 2 willfirstly be described.

Starting with FIG. 1, the projection objective 10 is transformed asfollows into its dry configuration. The immersion medium 26 is removedfrom the image space in a first step. This measure does not change thecorrection state before entry into the terminal element or into the lastoptical element 20 and at the exit of the terminal element 20. However,by removing the highly refractive, plane-parallel layer made from theimmersion medium 26 from the image space, the overcorrecting effectthereof is taken away such that the correction state in the image plane15 corresponds to the undercorrected correction state at the exitsurface 22.

In a further step, the thickness of the last optical element 20 isenlarged. In this case, the overcorrecting effect thereof increases withthe rising thickness. In accordance with the refractive index of theplate material, the thickness is selected to be so wide that theovercorrection effected by the thicker plate, which now forms the lastoptical element 20, largely compensates the undercorrected correctionstate at the entrance to the last optical element 20.

In two further steps, a larger working distance 24 by comparison withthe immersion configuration in FIG. 1 is set by axially displacing thelast optical element 20 in the direction of the first group 18. This canbe performed by axially displacing the last optical element 20 with theaid of a z-manipulator that can be driven electrically or in anotherway. It is also possible to mount the last optical element 20individually and to use spacers to set a suitable spacing between themounts of the first group 18 and the mount of the last optical element20 by removing and/or installing spacers. Since the plane-parallel plate20 is as free from refractive power as possible and does not sag, thisaxial displacement can be carried out without this having a measurableinfluence on the aberrations of the projection objective 10.

Furthermore, at least one of the lenses, for example the negative lens18 b, in the first group 18 is mounted such that it can be displacedaxially with the aid of a z-manipulator. A residual error can becompensated in this case by slightly displacing the lens 18 b in thedirection of the object plane such that the completely tuned projectionobjective 10 in dry configuration has a sufficiently good correctionstate at the light exit.

The last-mentioned step, specifically the fine tuning with the aid of atleast one manipulatable or variable optical element of the first group18 can frequently be required in order to be able to meet tightspecifications. In the event of lesser requirements, the first-mentionedsteps (changing the refractive index in the image space by introducingor removing an immersion medium, varying the thickness of the lastelement 20, and displacing the last element 20 in order to change theworking distance 24) can suffice in order to achieve a reconfigurationbetween immersion configuration and dry configuration (or vice versa).

It is described below how a disturbance or interference in the form of atemperature change affects the projection objective 10 in dryconfiguration (FIG. 2), and how the same disturbance affects theprojection objective 10 in immersion configuration (FIG. 1), and howaberrations induced by the disturbance can be corrected.

Firstly, the fact is that the response of the projection objective 10 toan identical disturbance in the dry configuration and in the immersionconfiguration is virtually identical if, firstly, the presence of theimmersion medium 26 is discounted. Such disturbance is encountered withthe projection objective 10 in the dry configuration by adjusting theposition of the substrate 14 in the direction of the optical axis 16 inorder thereby to carry out a focus correction such that the Zernikecoefficient Z4 vanishes in the middle of the field.

A displacement of the substrate 14 in the direction of the optical axis16 by the amount ΔZ (compare FIGS. 1 and 2) leads in both systems to awavefront change OPD for which it holds that:

$\begin{matrix}{{{OPD}_{\Delta \; z}(\rho)} = {\Delta \; {z \cdot n}{\sqrt{1 - {\left( \frac{NA}{n} \right)^{2}\rho^{2}}}.}}} & (1)\end{matrix}$

Here, n is the refractive index at the working distance 24, that is tosay n≈1.000 for air in the dry configuration, or n≈1.437 for water inthe immersion configuration for a given wavelength λ=193 nm. ρ is thenormalized radial pupil coordinate.

The wavefront change OPD Δz in accordance with equation (1) can bedeveloped in the customary way using Zernike polynomials:

OPD _(Δz)(ρ)=Δz·(f ₄(NA,n)·Z4(ρ)+f ₉(NA,n)·Z9(ρ)+f ₁₆(NA,n)·Z16(ρ)+f₂₅(NA,n)·Z25(ρ)+f ₃₆(NA,n)·Z36(ρ))  (2)

The following Zernike coefficients Δz·f_(i)(NA, n) with NA′=NA/n arethen yielded analytically in this expansion:

$\begin{matrix}{\mspace{79mu} {{f_{4}\left( {{NA},n} \right)} = {n \cdot \frac{4 - {NA}^{\prime 2} - {\sqrt{1 - {NA}^{\prime 2}}\left( {4 - {3\; {NA}^{\prime 2}} - {NA}^{\prime 4}} \right)}}{\frac{5}{2}{NA}^{\prime 4}}}}} & (3) \\{\mspace{79mu} {{f_{9}\left( {{NA},n} \right)} = {n \cdot \frac{\begin{matrix}{48 - {84\; {NA}^{\prime 2}} + {35\; {NA}^{\prime 4}} -} \\{\sqrt{1 - {NA}^{\prime 2}}\left( {48 - {60\; {NA}^{\prime 2}} + {11\; {NA}^{\prime 4}} + {NA}^{\prime 6}} \right)}\end{matrix}}{\frac{21}{2}{NA}^{\prime 6}}}}} & (4) \\{\mspace{79mu} {{f_{16}\left( {{NA},n} \right)} = {n \cdot \frac{\begin{matrix}{320 - {720\; {NA}^{\prime 2}} + {504\; N^{\prime 4}} - {105\; {NA}^{\prime 6}} -} \\{\sqrt{1 - {NA}^{\prime 2}}\begin{pmatrix}{320 - {560\; {NA}^{\prime 2}} + {264\; {NA}^{\prime 4}} -} \\{{23\; {NA}^{\prime 6}} - {NA}^{\prime 8}}\end{pmatrix}}\end{matrix}}{\frac{45}{2}{NA}^{\prime 8}}}}} & (5) \\{{f_{25}\left( {{NA},n} \right)} = {{n \cdot \frac{\begin{matrix}{1792 - {4928\; {NA}^{\prime 2}} + {4752\; {NA}^{\prime 4}} -} \\{{1848\; {NA}^{\prime 6}} + {231\; {NA}^{\prime 8}}}\end{matrix}}{\frac{77}{2}{NA}^{\prime 10}}} - {{n \cdot \sqrt{1 - {NA}^{\prime 2}}}\frac{\begin{pmatrix}{1792 - {4032\; {NA}^{\prime 2}} + {2960\; {NA}^{\prime 4}} -} \\{{760\; {NA}^{\prime 6}} + {39\; {NA}^{\prime 8}} + {NA}^{\prime 10}}\end{pmatrix}}{\frac{77}{2}{NA}^{\prime 10}}}}} & (6) \\{{f_{36}\left( {{NA},n} \right)} = {{n \cdot \frac{\begin{matrix}{9216 - {29952\; {NA}^{\prime 2}} + {36608\; {NA}^{\prime 4}} -} \\{{20592\; {NA}^{\prime 6}} + 5148^{\prime 8} - {429\; {NA}^{\prime 10}}}\end{matrix}}{\frac{117}{2}{NA}^{\prime 12}}} - {{n \cdot \sqrt{1 - {NA}^{\prime 2}}}\frac{\begin{pmatrix}{9216 - {25344\; {NA}^{\prime 2}} + {25088\; {NA}^{\prime 4}} -} \\{{10640\; {NA}^{\prime 6}} + {1740\; {NA}^{\prime 8}} - {59\; {NA}^{\prime 10}} - {NA}^{\prime 12}}\end{pmatrix}}{\frac{117}{2}{NA}^{\prime 12}}}}} & (7)\end{matrix}$

It is to be seen from equations (3) to (7) that the Zernike coefficientsΔz·f_(i), that is to say the induced spherical aberrations both of orderZ4 and of higher orders Z9, Z16, Z25, Z36 are a function both of thenumerical aperture and, in particular, of the refractive index n in theworking distance 24.

FIG. 3 illustrates this state of affairs with reference to a numericalexample. The bar diagram illustrates the wavefront changes, codedaccording to the Zernike coefficients Z4, Z9, Z16, Z25 and Z36 for adisplacement of the substrate 14 by Δz=1 μm given a numerical apertureNA=0.93 for the projection objective in dry configuration (FIG. 2) andfor the projection objective 10 in immersion configuration (FIG. 1). Ofeach pair of bars, the left-hand bar relates to the dry configuration,and the right-hand bar to the immersion configuration.

FIG. 4 illustrates the relative wavefront changes in the orders Z9, Z16,Z25 and Z36 referred to Z4. It follows in particular from FIG. 4 that adisplacement of the substrate 14 in the direction of the optical axis 16by the amount Δz has a lesser effect on the wavefront changes in thehigher orders Z9, Z16, Z25, Z36 with the projection objective 10 inimmersion configuration than in the dry configuration. That is to say,the sensitivity of the projection objective 10 to the z-displacement ofthe substrate 14 in the higher Zernike coefficients is less in immersionconfiguration than in the dry configuration. The consequence of this isthat the method of focus correction by displacing the substrate 14 inthe direction of the optical axis 16 that is applied in the dryconfiguration of the projection objective 10 has less influence on thewavefront changes or aberrations of higher order.

While previously the different focus sensitivities of the projectionobjective 10 in the dry configuration have been considered by comparisonwith the immersion configuration, in the following the sensitivity ofthe projection objective 10 in both configurations is explained withregard to a disturbance in the form of a temperature change.

In a simulation of aberrations induced by a global, homogeneoustemperature change, for example in the air (or another gas) around theprojection objective 10, in the projection objective housing with theindividual mounts, in the gas inside the projection objective 10, in thelenses and in the immersion liquid 24, the sensitivities of thefollowing effects were considered:

-   1. Change in the lens geometries—that is to say the thicknesses and    radii—through the thermal expansion of the lens material;-   2. Changes in spacings through the thermal expansion of the    projection objective housing (metal mounts):    -   a. between the lenses (“air spaces”),    -   b. between the pattern 12 (reticle) and a first optical element        of the first group 18 of optical elements,    -   c. between the last optical element 20 and the substrate 14;-   3. Changes in refractive index Δn=dn/dT ΔT of the lens material    (quartz, CaF₂);-   4. Changes in refractive index Δn=dn/dT ΔT    -   a. of the gas between the individual optical elements of the        first group 18,    -   b. of the air (or the other gas) between the pattern 12 and the        first optical element of the group 18,    -   c. in the immersion liquid 24 between the last optical element        20 and the substrate 14 in the immersion system or in the air        (or the other gas) in the case of the dry system.

FIG. 5 shows the temperature sensitivities without focus correction,that is to say without displacement of the substrate 14 in the directionof the optical axis with reference to the spherical Zernike coefficientsin the center of the field in a comparison between the projectionobjective 10 in the dry configuration and the projection objective 10 inthe immersion configuration, once again the left-hand bar of each pairof bars referring to the dry configuration, and the right-hand barreferring to the immersion configuration.

It emerges from FIG. 5 that the dry configuration and the immersionconfiguration of the projection objective 10 differ considerably fromone another with regard to the temperature sensitivities, at least inthe orders Z4 and Z9. These differences between the dry configurationand the immersion configuration result from the above-mentionedcontributions 2.c and 4.c to the temperature effects, that is to say thedifferences are a consequence of the presence of the immersion liquid 26at the working distance 24 between the last optical element 20 and thesubstrate 14. Of the two contributions 2.c and 4.c, the contribution2.c, that is to say the change in the working distance 24, is thedominating additional contribution to the aberrations in the immersionconfiguration. This can be explained in that the temperature-inducedthermal expansion of the projection objective 10 displaces the lastoptical element 20 in the direction of the substrate 14. The workingdistance 24 is consequently reduced. Whereas this has no influence onthe aberrations in the dry configuration, the change in the workingdistance 24 in the immersion configuration induces a changed layerthickness of the immersion liquid 26 that induces additionalaberrations. All other above-mentioned contributions to the temperatureeffects yield virtually identical sensitivities in the two systems.

FIG. 6 illustrates with the aid of a further bar diagram the extent towhich the previously described aberrations induced by a temperaturechange can be compensated only by adjusting the position of thesubstrate 14 in the direction of the optical axis 16.

FIG. 6 shows the wavefront changes OPD/T, caused by temperature changes,for the dry configuration and for the immersion configuration,respectively without and with focus correction solely by displacing thesubstrate 14 in the direction of the optical axis, in a fashion split upwith reference to the Zernike coefficients Z9, Z16, Z25, Z36 (Z4=0 afterthe focus correction).

Of the four bars relating to each of the coefficients Z9, Z16, Z25, Z36,the first bar relates to the dry configuration without focus correction,the second bar to the dry system with focus correction (Z4=0), the thirdbar to the immersion configuration without focus correction, and thefourth bar to the immersion configuration with focus correction (Z4=0)solely by displacing the substrate 14 in the direction of the opticalaxis.

It is clear from FIG. 6 that in the dry configuration the higherspherical sensitivities Z9, Z16, Z25, Z36 relating to a homogeneoustemperature change have a similar ratio to the Z4 fraction as the focussensitivities in the case of adjusting the position of the substrate 14in the direction of the optical axis 16. As a result of thiscircumstance, a focus correction, that is to say a correction such thatZ4=0 in the middle of the field, solely by adjusting the position of thesubstrate 14 in the direction of the optical axis simultaneously alsoadequately corrects substantial contributions of the higher sphericalaberrations Z9, Z16, Z25, Z36 in the dry configuration. By contrast, inthe immersion configuration the crosstalk in the higher sphericalZernike coefficients is substantially smaller in the case of Z4correction solely by adjusting the position of the substrate 14, as hasbeen explained above with reference to FIGS. 3 and 4. The consequence ofthis is that in the case of a complete compensation of Z4 in theimmersion configuration it is still only small fractions of the higherZernike coefficients Z9, Z16, Z25, Z36 that are also compensated, andtherefore large fractions of these aberrations of higher order remain asresidual errors. Consequently, it is not sufficient to correctaberrations simply by adjusting the position of the substrate 14 in thedirection of the optical axis, that is to say nothing but a focuscorrection to Z4=0 in the immersion configuration. This means that inthe immersion configuration as contrasted with the dry configuration forthe case of an identical temperature change there remains a residualerror Z9 that is larger by a factor of approximately 7 and residualerrors that are approximately four to five times larger for the otherspherical Zernike coefficients of higher order when only one focuscorrection is performed by adjusting the position of the substrate 14.

With reference to FIGS. 7 a) and b), it is described below how theresidual errors of the projection objective 10 can be reduced inimmersion configuration by means of an alternative type of focusing.

FIG. 7 a) shows the projection objective 10 in accordance with FIG. 1 inthe region of the last optical element 20 and of the penultimate opticalelement 18 c that forms the last optical element of the first group 18of optical elements of the projection objective 10. The space betweenthe penultimate optical element 18 c and the last optical element 20 isfilled with a gas having a refractive index n of approximately 1.

In accordance with FIG. 7 b), the projection objective 10 has apositioning device 28 that comprises an actuator 30 and a measuringdevice 32. The actuator 30 is capable of positioning the last opticalelement 20 in the direction of the optical axis 16 (z direction) as isindicated by an arrow 30 a. The actuator 30 is further capable oflikewise positioning the substrate 14 in the direction of the opticalaxis 16, as indicated by an arrow 30 b.

The actuator 30 is capable, in particular, of adjusting the position ofthe last optical element 20 and of the substrate 14 in a mutuallycorrelated ratio in the direction of the optical axis 16.

The aim firstly is to discuss what is the result of a common adjustmentof the position of the last optical element 20 and of the substrate 14in the same direction in a ratio of 1:1 as is illustrated in FIG. 7 b)by comparison with FIG. 7 a).

Adjusting the position of the last optical element 20 enlarges the airspace 34 between the penultimate optical element 18 c and the lastoptical element 20 by the amount Δz_(LR) when the optical element 20 isdisplaced by the amount Δz (just like the substrate 14).

The wavefront change OPD_(Δz,LR) owing to the enlargement of the airspace 34 is then given by

OPD _(Δz,LR)(ρ)=Δz·n′√{square root over (1−(NA/n′)²ρ²)}  (8)

Here, n′ is the refractive index of the gas in the air space 34 upstreamof the last optical element 20. Comparing equation (8) with equation (1)shows that this type of focusing in the projection objective 10 inimmersion configuration leads to the same change in the wavefront asdoes a corresponding sole displacement of the substrate 14 in the dryconfiguration, since the refractive index n′˜1 in the last air space 34upstream of the last optical element 20 is virtually identical to therefractive index n˜1 of the air in the dry system. Consequently, theprojection objective 10 in the dry configuration and in the immersionconfiguration then have the same focus sensitivities (equations (2) to(7)) with the same crosstalk to the higher spherical Zernikecoefficients Z9, Z16, Z25, Z36.

FIG. 8 shows a similar illustration to that in FIG. 6, the fourth bar inrelation to each of the Zernike coefficients Z9, Z16, Z25, Z36 showingthe residual aberrations for the projection objective 10 in immersionconfiguration after an identical displacement of the last opticalelement 20 and of the substrate 14.

Comparing this respective fourth bar with the respective fourth bar inFIG. 6 shows that the residual aberrations in the higher Zernikecoefficients Z9, Z16, Z25, Z36 are substantially reduced, and differfrom the residual aberrations in the dry configuration only by factorsof approximately 1.7 to 2.7.

It is described below how the residual aberrations of the projectionobjective 10 in the immersion configuration can be yet further reduced.

A further reduction in the residual aberrations of the projectionobjective 10 in immersion configuration is achieved by setting theworking distance 24 between the last optical element 20 and thesubstrate 14 solely by adjusting the position of the last opticalelement 20 to a nominal value (nominal working distance), somethingwhich can likewise be carried out with the aid of the actuator 30. Thenominal value can in this case be the originally set optimum workingdistance in immersion configuration if no disturbance such as atemperature-induced expansion of the system is present.

The wavefront change OPD_(Δz,LLE) owing to displacement of the lastoptical element 20 by the path Δz in the direction of the optical axisis then yielded as the difference between the wavefront changeOPD_(Δz,LR) by enlarging the last air space 34 (FIG. 7 b)) and thewavefront change OPD_(Δz,S) by adjusting the position of the substrate14 in the direction of the optical axis 16:

$\begin{matrix}\begin{matrix}{{{OPD}_{{\Delta \; z},{LLE}}(\rho)} = {{{OPD}_{{\Delta \; z},{LR}}(\rho)} - {{OPD}_{{\Delta \; z},S}(\rho)}}} \\{= {\Delta \; {z\begin{bmatrix}{{{n^{\prime}}^{~}\sqrt{1 - {\left( {{NA}/n^{\prime}} \right)^{2}\rho^{2}}}} -} \\{n\sqrt{1 - {\left( {{NA}/n} \right)^{2}\rho^{2}}}}\end{bmatrix}}}}\end{matrix} & (9)\end{matrix}$

Here, n is the refractive index of the immersion medium 26, and n′ isthe refractive index of the gas in the air space 34 upstream of the lastoptical element 20.

The (sole) adjustment of the position of the last optical element 20 cannow be used to fully compensate again the displacement of the lastoptical element 20 in the direction of the substrate 14 induced by thethermal expansion of the projection objective 10.

The result of this mode of procedure is illustrated in FIG. 9.

FIG. 9 shows for the first bar (seen from the left) relating to eachZernike coefficient Z9, Z16, Z25, Z36 the aberrations of a projectionobjective 10 in dry configuration due to a disturbance in the form of atemperature change, no focus correction yet having been performed. (TheZernike coefficient Z4, which is not shown in this figure, does notvanish here.)

The respective second bar in FIG. 9 shows the residual aberrations ofthe projection objective 10 in dry configuration after a focuscorrection solely by displacing the substrate 14 in the direction of theoptical axis 16. (The Zernike coefficient Z4, which is not shown in thisfigure, vanishes here.)

The respective third bar in FIG. 9 shows in relation to each Zernikecoefficient Z9, Z16, Z25, Z36 the aberrations of the projectionobjective 10 in immersion configuration due to a disturbance in the formof a temperature change without focus correction, the fourth bar showsthe aberrations after setting the working distance 24 between the lastoptical element 20 and the substrate 14 to a desired working distancethat corresponds, or can correspond, to the originally set workingdistance before commissioning of the projection objective 10, and thefifth bars show the residual aberrations after additional commonadjustment of the position of the last optical element 20 and of thesubstrate 14 in the direction of the optical axis in the ratio of 1:1.

Comparing the first and fourth bars relating to each Zernike coefficientin FIG. 9 reveals that restoring the desired working distance betweenthe last optical element 20 and the substrate 14 yields sensitivitiesthat are virtually identical to the not refocused sensitivities of theprojection objective 10 in dry configuration.

Comparing the second and fifth bars in relation to each Zernikecoefficient in FIG. 9 reveals that these show identical residualaberrations for the projection objective 10 in dry configuration afterfocus correction, and identical residual aberrations for the projectionobjective 10 in immersion configuration after adjusting the position ofthe last optical element 20 in order to set a desired working distance,and identical adjustment of the position of the last optical element 20and of the substrate 14 in the direction of the optical axis 16.

The focus correction (Z4=0) is carried out by correlated adjustment ofthe position of the last optical element 20 and the substrate 14. Thisnow results in the same corrective action as in the case of theprojection objective 10 in dry configuration (identical focussensitivities), and virtually identical and sufficiently small residualerrors of the higher spherical aberrations are achieved.

During operation of the projection objective 10 in immersionconfiguration, the working distance 24 can be controlled by means of themeasuring device 32, and it is then possible on the basis of therespective measurement results to use the actuator 30 to keep theworking distance 24 at the desired working distance, in the manner of acontrol loop.

FIG. 10 illustrates diagrammatically an embodiment with the aid ofwhich, on the basis of a specific mounting technique for the lastoptical element 20, it is already possible to keep the working distance24 between the last optical element 20 and the substrate 14 withreference to temperature changes at the set point, or to position thelast optical element 20 for the purpose of minimizing aberrations.

The last optical element 20 is held in a mount 20 a that is connected toa mount 19 of an optical element of the first group 18 of opticalelements of the projection objective 10 at a point 21. The mount 20 ahas, in particular, a thermal expansion coefficient that is large bycomparison with the thermal expansion coefficient of the mount 19.

If, by heating up, the mount 19 now expands in the direction of an arrow23, this would reduce the working distance 24. However, owing to theheating up the mount 20 a also expands, but in the opposite sense to theexpansion of the mount 19 in accordance with an arrow 25, the resultbeing not to diminish the working distance 24 but to keep itsubstantially constant. It is thereby possible to keep the workingdistance 24 at the nominal value.

However, it is also possible to provide not to keep the working distance24 at the nominal value by means of the previously described mountingtechnique, but to fashion the mount 20 a for the last optical element 20such that it not only compensates the change in the working distance 24,but overcompensates it in such a way that the above-described customaryfocus correction, that is to say solely adjusting the position of thesubstrate 14, leads again to the same results for the correction ofaberrations. Thus, with this mode of procedure the temperaturesensitivities of the projection objective are adapted in terms of designin such a way that they are once again compatible with the focussensitivities as in the dry configuration.

The following measures are provided with reference, again, to FIGS. 1and 2, which show the projection objective 10 in immersion configurationand in dry configuration, respectively, in order to tune the projectionobjective 10 between the dry configuration and the immersionconfiguration.

A large distance that enables a substantial axial displacement of thelast optical element 20 exists between the first group 18 and the lastoptical element 20.

The tunability between the immersion configuration in FIG. 1 and the dryconfiguration in FIG. 2 of the projection objective 10 is preferablyachieved with the aid of a variation in the thickness of the lastoptical element 20, preferably in conjunction with a displacement of thelast optical element 20 relative to the image plane 15, it beingnecessary, however, not to confuse this method with the previouslydescribed method for correcting aberrations of the projection objective10 in the immersion configuration.

The last optical element 20 is, furthermore, exchangeable.

The last optical element 20 can have a variable thickness, the lastoptical element 20 preferably having a thickness that can be variedwithout removing material or adding material. This is preferablyachieved by virtue of the fact that the last optical element 20comprises a number of mutually detachable components that are arrangedat a spacing from one another or are neutrally interconnected in opticalterms, it being preferred for components of the last optical element 20to consist of different optical materials, preferably at least onecomponent consisting of fluoride crystal, in particular of lithiumfluoride or calcium fluoride.

The optical material, adjacent to the exit surface 22, of the lastoptical element 20 preferably has a refractive index n_(E) that is closeto the refractive index n_(I) of the immersion medium 26, it beingpreferred for a ratio n_(I)/n_(E) to be more than 0.8, in particularmore than 0.9.

Furthermore, the first group 18 of optical elements also has at leastone displaceable optical element, but preferably a number of, inparticular at least five, displaceable optical elements, at least one ofthe displaceable optical elements being displaceable along the opticalaxis 16.

A free space upstream of the previously mentioned displaceable elementand/or downstream of the displaceable element is in this case preferablydimensioned to be so large that displacing the at least one displaceableoptical element renders it possible to correct at least a fraction ofaberrations that result from adapting the last optical element 20 to theimmersion medium 26. The projection objective 10 can be assigned atleast one exchangeable optical correction element that preferably has atleast one aspheric surface. Furthermore, at least one optical element ofthe first group 18 can have at least one optical surface with a surfacecurvature that can be varied reversibly or permanently.

The projection objective 10 is designed such that, when use is made ofthe immersion medium 26, that is to say in the immersion configuration,it has an image-side numerical aperture NA<1 between exit surface 22 andimage plane 15, the image-side numerical aperture preferably beingbetween approximately 0.7 and 1.0, in particular between 0.8 and 1.0.

It is further provided that the last optical element 20 can be removedfrom the projection objective 10 and be replaced by a plane-parallelplate that is large by comparison with the exit surface of theprojection objective 10 and can be laid over a large area of thesubstrate 14 to be exposed.

FIGS. 11 and 12 demonstrate particular exemplary embodiments ofprojection objectives in the case of which the present invention can beimplemented.

FIG. 11 shows by way of example a purely refractive, rotationallysymmetrical projection objective 40 for high-resolutionmicrolithography, in particular in the DUV wavelength region. In FIG.11, 41 designates the optical axis of the projection objective 40, 42denotes the object plane, 43 denotes the image plane, 44 denotes thefirst group of optical elements, 45 denotes the last optical element,and 46 denotes the immersion medium. Table 1 (appended) summarizes thespecification of the design of the projection objective 40 in tabularform. In this case, column 1 specifies the number of refractive surfacesor surfaces otherwise distinguished, column 2 specifies the radius ofthe surfaces (in mm), column 3 specifies the distance, designated asthickness, of the surface from the subsequent surface (in mm), column 4specifies the material, column 5 specifies the refractive index of thematerial at the operating wavelength, and column 6 specifies the maximumuseful radius (half the free diameter). The total length L between theobject plane and image plane is approximately 1.166 mm. All curvaturesare spherical. FIG. 11 shows the projection objective 40 in immersionconfiguration, and the data in table 1 likewise correspond to theimmersion configuration. Table 2 contains the data of the projectionobjective in dry configuration.

FIG. 12 illustrates a catadioptric projection objective 50 in the caseof which the present invention can likewise be used. The catadioptricprojection objective 50 with geometric beam splitter 52 is provided forthe purpose of imaging a pattern lying in its object plane 53 into theimage plane 56 to the scale 4:1 while producing a real intermediateimage 54 in the image plane 56. The optical axis 58 is folded at thegeometric beam splitter 52 in order to be able to make use when imagingof a concave mirror 60 that facilitates the chromatic correction of theoverall system. FIG. 12 and table 3 reproduce the properties of theprojection objective 50 in the immersion configuration. Table 4 containsthe data of the corresponding dry configuration.

The data of the projection objective 50 are listed in table 5, thesurface 32 being formed by a nanosphere.

TABLE 1 j29o REFRACTIVE INDEX ½ FREE SURFACE RADII THICKNESSES LENSES248.38 nm DIAMETER 0 0.000000000 32.000000000 1.00000000 54.410 10.000000000 10.587540450 L710 0.99998200 61.093 2 −2417.35176712013.126300000 SUPRA1 1.50833811 63.132 3 −248.195466920 7.359264018 L7100.99998200 63.945 4 −168.131361870 10.000000000 SUPRA1 1.50833811 64.2025 328.986124739 7.907519166 L710 0.99998200 70.046 6 671.74215274322.614900000 SUPRA1 1.50833811 71.945 7 −219.346865952 1.054978296 L7100.99998200 73.402 8 351.854459479 21.378800000 SUPRA1 1.50833811 77.4499 −417.329819985 0.748356148 L710 0.99998200 77.668 10 266.25924201726.426700000 SUPRA1 1.50833811 76.971 11 −418.068287643 0.747164758 L7100.99998200 75.964 12 195.049526899 10.000000000 SUPRA1 1.50833811 69.81613 112.784218098 27.264697553 L710 0.99998200 64.221 14 −548.97630502010.000000000 SUPRA1 1.50833811 63.660 15 167.581609987 25.042515270 L7100.99998200 61.992 16 −203.629259785 10.000000000 SUPRA1 1.5083381162.349 17 360.120642869 28.995838980 L710 0.99998200 66.965 18−127.653905514 12.696400000 SUPRA1 1.50833811 68.153 19 −1103.72572497017.018787360 L710 0.99998200 81.984 20 −225.898831342 23.521200000SUPRA1 1.50833811 84.684 21 −171.063497139 1.574450554 L710 0.9999820092.606 22 −22770.163604600 38.438000000 SUPRA1 1.50833811 109.997 23−229.816390281 0.749282985 L710 0.99998200 113.270 24 1170.59463054038.363100000 SUPRA1 1.50833811 123.579 25 −320.184892150 0.749629640L710 0.99998200 124.514 26 335.012872058 39.596800000 SUPRA1 1.50833811124.658 27 −764.462984962 2.214257730 L710 0.99998200 123.947 28270.136227728 25.935800000 SUPRA1 1.50833811 112.963 29 1248.6180775104.352014987 L710 0.99998200 110.825 30 177.098661261 18.578800000 SUPRA11.50833811 96.632 31 131.459110961 48.405871098 L710 0.99998200 84.99732 −254.431714105 10.000000000 SUPRA1 1.50833811 83.694 33 149.73419211349.515509852 L710 0.99998200 77.858 34 −137.204786283 10.000000000SUPRA1 1.50833811 78.232 35 1410.223675540 43.391488727 L710 0.9999820089.345 36 −134.825941720 35.292100000 SUPRA1 1.50833811 91.736 37−168.418502871 3.480235112 L710 0.99998200 110.924 38 −350.80598926924.010800000 SUPRA1 1.50833811 123.372 39 −244.301424027 6.015284795L710 0.99998200 128.258 40 4941.534628580 43.549100000 SUPRA1 1.50833811147.192 41 −357.889527255 2.367042190 L710 0.99998200 149.417 421857.663670230 40.932000000 SUPRA1 1.50833811 156.043 43 −507.091567715−0.213252954 L710 0.99998200 156.763 44 0.000000000 0.962846248 L7100.99998200 155.516 45 637.188120359 28.431900000 SUPRA1 1.50833811156.869 46 −4285.746531360 0.749578310 L710 0.99998200 156.617 47265.928249908 45.432900000 SUPRA1 1.50833811 152.353 48 1127.17032967057.049328626 L710 0.99998200 150.272 49 −273.057181282 24.571800000SUPRA1 1.50833811 149.389 50 −296.450446798 2.401860529 L710 0.99998200150.065 51 −317.559071036 23.847600000 SUPRA1 1.50833811 148.110 52−297.103672940 0.819938446 L710 0.99998200 148.158 53 223.86919277528.117900000 SUPRA1 1.50833811 122.315 54 548.591751129 0.749776549 L7100.99998200 120.110 55 123.937471688 34.861300000 SUPRA1 1.5083381199.291 56 211.883788830 0.738299719 L710 0.99998200 93.879 57121.391085072 21.109500000 SUPRA1 1.50833811 82.929 58 178.11054149813.722409422 L710 0.99998200 77.266 59 314.102464129 10.000000000 SUPRA11.50833811 71.524 60 60.563892001 10.471596266 L710 0.99998200 49.697 6171.706607533 10.069000000 SUPRA1 1.50833811 48.032 62 53.1842423170.713865261 L710 0.99998200 40.889 63 48.728728866 24.194000000 SUPRA11.50833811 39.865 64 325.049018458 16.249640231 L710 0.99998200 35.97965 0.000000000 3.000000000 SUPRA1 1.50833811 16.879 66 0.0000000002.000000000 IMMERS 1.40000000 14.998 67 0.000000000 0.0000000001.00000000 13.603

TABLE 2 j30o REFRACTIVE INDEX ½ FREE SURFACE RADII THICKNESSES LENSES248.38 nm DIAMETER 0 0.000000000 32.000000000 1.00000000 54.410 10.000000000 10.283889256 L710 0.99998200 61.093 2 −2417.35176712013.126300000 SUPRA1 1.50833811 63.069 3 −248.195466920 7.293007084 L7100.99998200 63.884 4 −168.131361870 10.000000000 SUPRA1 1.50833811 64.1375 328.986124739 8.273191790 L710 0.99998200 69.971 6 671.74215274322.614900000 SUPRA1 1.50833811 72.045 7 −219.346865952 0.447882685 L7100.99998200 73.489 8 351.854459479 21.378800000 SUPRA1 1.50833811 77.4199 −417.329819985 0.643718463 L710 0.99998200 77.636 10 266.25924201726.426700000 SUPRA1 1.50833811 76.935 11 −418.068287643 1.297611013 L7100.99998200 75.923 12 195.049526899 10.000000000 SUPRA1 1.50833811 69.62713 112.784218098 26.146948060 L710 0.99998200 64.049 14 −548.97630502010.000000000 SUPRA1 1.50833811 63.646 15 167.581609987 26.480913850 L7100.99998200 61.963 16 −203.629259785 10.000000000 SUPRA1 1.5083381162.465 17 360.120642869 28.474843347 L710 0.99998200 67.077 18−127.653905514 12.696400000 SUPRA1 1.50833811 68.070 19 −1103.72572497017.347391549 L710 0.99998200 81.856 20 −225.898831342 23.521200000SUPRA1 1.50833811 84.765 21 −171.063497139 1.525859924 L710 0.9999820092.671 22 −22770.163604600 38.438000000 SUPRA1 1.50833811 110.016 23−229.816390281 0.449372011 L710 0.99998200 113.280 24 1170.59463054038.363100000 SUPRA1 1.50833811 123.463 25 −320.184892150 0.449220757L710 0.99998200 124.404 26 335.012872058 39.596800000 SUPRA1 1.50833811124.508 27 −764.462984962 0.448529485 L710 0.99998200 123.785 28270.136227728 25.935800000 SUPRA1 1.50833811 113.275 29 1248.6180775104.599063715 L710 0.99998200 111.173 30 177.098661261 18.578800000 SUPRA11.50833811 96.787 31 131.459110961 48.903368693 L710 0.99998200 85.12332 −254.431714105 10.000000000 SUPRA1 1.50833811 83.644 33 149.73419211349.544589669 L710 0.99998200 77.792 34 −137.204786283 10.000000000SUPRA1 1.50833811 78.174 35 1410.223675540 43.113042129 L710 0.9999820089.233 36 −134.825941720 35.292100000 SUPRA1 1.50833811 91.558 37−168.418502871 4.049119334 L710 0.99998200 110.696 38 −350.80598926924.010800000 SUPRA1 1.50833811 123.308 39 −244.301424027 5.341877309L710 0.99998200 128.188 40 4941.534628580 43.549100000 SUPRA1 1.50833811146.729 41 −357.889527255 4.028668923 L710 0.99998200 148.997 421857.663670230 40.932000000 SUPRA1 1.50833811 155.818 43 −507.091567715−1.371361371 L710 0.99998200 156.540 44 0.000000000 2.120040201 L7100.99998200 155.343 45 637.188120359 28.431900000 SUPRA1 1.50833811156.764 46 −4285.746531360 0.447699567 L710 0.99998200 156.510 47265.928249908 45.432900000 SUPRA1 1.50833811 152.266 48 1127.17032967056.966580248 L710 0.99998200 150.172 49 −273.057181282 24.571800000SUPRA1 1.50833811 149.291 50 −296.450446798 2.661459751 L710 0.99998200149.961 51 −317.559071036 23.847600000 SUPRA1 1.50833811 147.915 52−297.103672940 0.449161173 L710 0.99998200 147.956 53 223.86919277528.117900000 SUPRA1 1.50833811 122.290 54 548.591751129 1.339172987 L7100.99998200 120.081 55 123.937471688 34.861300000 SUPRA1 1.5083381199.087 56 211.883788830 0.952940583 L710 0.99998200 93.588 57121.391085072 21.109500000 SUPRA1 1.50833811 82.604 58 178.11054149813.676325222 L710 0.99998200 76.860 59 314.102464129 10.000000000 SUPRA11.50833811 71.076 60 60.563892001 10.077651049 L710 0.99998200 49.477 6171.706607533 10.069000000 SUPRA1 1.50833811 47.911 62 53.1842423170.732248727 L710 0.99998200 40.780 63 48.728728866 24.194000000 SUPRA11.50833811 39.753 64 325.049018458 4.167687088 L710 0.99998200 35.772 650.000000000 5.000000000 SUPRA1 1.50833811 32.831 66 0.00000000012.000000000 L710 0.99998200 29.694 67 0.000000000 0.0000000001.00000000 13.603

TABLE 3 j31o REFRACTIVE INDEX ½ FREE SURFACE RADII THICKNESSES LENSES157.63 nm DIAMETER  0 0.000000000 38.482288093 1.00000000 85.333  1304.292982078 22.168809366 CAF2HL 1.55840983 92.476  2 2741.79448105096.128678854 1.00000000 92.204  3 0.000000000 0.000000000 −1.00000000131.930 REFL  4 0.000000000 −467.095641350 −1.00000000 90.070  5199.893955036 −10.268444544 CAF2HL −1.55840983 91.280  6 486.702942680AS−26.734713685 −1.00000000 96.529  7 186.738998389 −10.064297945 CAF2HL−1.55840983 99.240  8 447.975139348 −19.001496621 −1.00000000 111.362  9243.529966034 19.001496621 1.00000000 114.369 REFL 10 447.97513934810.064297945 CAF2HL 1.55840983 112.384 11 186.738998389 26.7347136851.00000000 102.903 12 486.702942680AS 10.268444544 CAF2HL 1.55840983101.523 13 199.893955036 464.738613843 1.00000000 96.499 14 0.0000000000.000000000 −1.00000000 115.398 REFL 15 0.000000000 −100.235657635−1.00000000 92.746 16 −536.442986965 −25.379215206 CAF2HL −1.5584098394.306 17 629.049380815 −7.436012624 −1.00000000 93.787 18 0.000000000−118.304806660 −1.00000000 91.342 19 −312.177007433AS −24.720749191CAF2HL −1.55840983 94.928 20 −734.696609024 −220.443381712 −1.0000000094.168 21 −277.004238298AS −15.426909916 CAF2HL −1.55840983 96.206 22−460.130899964 −73.782961291 −1.00000000 95.245 23 −158.318468619−30.586960517 CAF2HL −1.55840983 91.460 24 −162.867000225 −41.632945268−1.00000000 84.793 25 419.508310212 −20.539965049 CAF2HL −1.5584098384.016 26 −238.581080262 −31.955227253 −1.00000000 85.006 27−430.197019246 −30.182066783 CAF2HL −1.55840983 92.237 28691.939037816AS −23.703096035 −1.00000000 93.527 29 −241.462660758AS−10.000000000 CAF2HL −1.55840983 97.681 30 −182.472613831 −25.656103361−1.00000000 96.159 31 −420.041190250 −36.705938298 CAF2HL −1.5584098398.541 32 324.867666879 −43.586137768 −1.00000000 99.096 33−44866.873107000 36.893151865 −1.00000000 93.979 34 −149.830817441−28.311419778 CAF2HL −1.55840983 94.246 35 −315.631878253AS−18.939811826 −1.00000000 91.369 36 −172.862510793 −12.271843841 CAF2HL−1.55840983 87.996 37 −115.635345524 −27.567353538 −1.00000000 81.847 38−229.213645994AS −32.436472831 CAF2HL −1.55840983 82.617 39474.721571790 −3.611495525 −1.00000000 81.971 40 −152.435372054−30.802088433 CAF2HL −1.55840983 75.907 41 −530.778945822 −8.465514650−1.00000000 70.966 42 −159.504999222 −41.060952888 CAF2HL −1.5584098363.576 43 3040.455878600 −4.225976128 −1.00000000 51.729 44−226.630329417AS −24.123224774 CAF2HL −1.55840983 44.179 45897.778633917 −8.617797536 −1.00000000 33.827 46 0.000000000−8.000000000 CAF2HL −1.55840983 22.352 47 0.000000000 −2.000000000IMMERS −1.39000000 18.217 48 0.000000000 0.000000000 −1.00000000 17.067ASPHERIC CONSTANTS SURFACE NO. 6 K 0.0000 C1 3.87858881e−009 C2−1.57703627e−013 C3 1.62703226e−017 C4 −1.12332671e−021 C5−1.51356191e−026 C6 8.57130323e−031 SURFACE NO. 12 K 0.0000 C13.87858881e−009 C2 −1.57703627e−013 C3 1.62703226e−017 C4−1.12332671e−021 C5 −1.51356191e−026 C6 8.57130323e−031 SURFACE NO. 19 K0.0000 C1 3.62918557e−009 C2 6.75596543e−014 C3 5.68408321e−019 C4−6.78832654e−023 C5 6.78338885e−027 C6 −2.05303753e−031 SURFACE NO. 21 K0.0000 C1 1.19759751e−008 C2 7.35438590e−014 C3 7.03292772e−019 C4−1.26321026e−023 C5 −3.01047364e−027 C6 2.08735313e−031 SURFACE NO. 28 K0.0000 C1 −8.39294529e−009 C2 −3.39607506e−013 C3 8.76320979e−018 C4−1.43578199e−021 C5 5.59234999e−026 C6 2.01810948e−030 SURFACE NO. 29 K0.0000 C1 1.74092829e−008 C2 −1.69607632e−013 C3 1.18281063e−017 C4−3.08190938e−021 C5 1.70082968e−025 C6 −1.68479126e−030 SURFACE NO. 35 K0.0000 C1 −2.14453018e−008 C2 6.73947641e−013 C3 −4.84677574e−017 C45.99264335e−021 C5 −2.87629386e−025 C6 3.90592520e−031 SURFACE NO. 38 K0.0000 C1 1.60415031e−008 C2 4.78837509e−015 C3 2.08320399e−016 C4−2.87713700e−020 C5 1.77485272e−024 C6 −1.93501550e−029 SURFACE NO. 44 K0.0000 C1 −6.56394686e−008 C2 −8.25210588e−012 C3 −1.27328625e−016 C4−1.16616292e−020 C5 −1.58133131e−023 C6 6.39526832e−027

TABLE 4 j32o REFRACTIVE INDEX ½ FREE SURFACE RADII THICKNESSES LENSES157.63 nm DIAMETER  0 0.000000000 36.500665837 1.00000000 85.333  1304.292982078 22.168809366 CAF2HL 1.55840983 92.166  2 2741.79448105096.128678854 1.00000000 91.891  3 0.000000000 0.000000000 −1.00000000131.415 REFL  4 0.000000000 −467.820384551 −1.00000000 89.765  5199.893955036 −10.268444544 CAF2HL −1.55840983 91.269  6 486.702942680AS−26.059978075 −1.00000000 96.632  7 186.738998389 −10.064297945 CAF2HL−1.55840983 99.260  8 447.975139348 −19.256116633 −1.00000000 111.485  9243.529966034 19.256116633 1.00000000 114.609 REFL 10 447.97513934810.064297945 CAF2HL 1.55840983 112.551 11 186.738998389 26.0599780751.00000000 103.039 12 486.702942680AS 10.268444544 CAF2HL 1.55840983101.801 13 199.893955036 465.028501331 1.00000000 96.752 14 0.0000000000.000000000 −1.00000000 115.771 REFL 15 0.000000000 −100.235657635−1.00000000 93.044 16 −536.442986965 −25.379215206 CAF2HL −1.5584098394.574 17 629.049380815 −8.746601911 −1.00000000 94.056 18 0.000000000−116.715874811 −1.00000000 91.368 19 −312.177007433AS −24.720749191CAF2HL −1.55840983 94.620 20 −734.696609024 −220.365529295 −1.0000000093.861 21 −277.004238298AS −15.426909916 CAF2HL −1.55840983 95.944 22−460.130899964 −74.636127671 −1.00000000 94.984 23 −158.318468619−30.586960517 CAF2HL −1.55840983 91.216 24 −162.867000225 −41.086604589−1.00000000 84.569 25 419.508310212 −20.539965049 CAF2HL −1.5584098383.832 26 −238.581080262 −32.443299462 −1.00000000 84.836 27−430.197019246 −30.182066783 CAF2HL −1.55840983 92.223 28691.939037816AS −22.851030925 −1.00000000 93.515 29 −241.462660758AS−10.000000000 CAF2HL −1.55840983 97.602 30 −182.472613831 −25.705407401−1.00000000 96.085 31 −420.041190250 −36.705938298 CAF2HL −1.5584098398.486 32 324.867666879 −7.220642187 −1.00000000 99.044 33−149.830817441 −28.311419778 CAF2HL −1.55840983 94.165 34−315.631878253AS −11.206528270 −1.00000000 91.678 35 0.000000000−7.539660426 −1.00000000 92.142 36 −172.862510793 −12.271843841 CAF2HL−1.55840983 88.327 37 −115.635345524 −27.665363620 −1.00000000 82.122 38−229.213645994AS −32.436472831 CAF2HL −1.55840983 82.891 39474.721571790 −3.783646156 −1.00000000 82.256 40 −152.435372054−30.802088433 CAF2HL −1.55840983 76.122 41 −530.778945822 −8.330902516−1.00000000 71.200 42 −159.504999222 −41.060952888 CAF2HL −1.5584098363.821 43 3040.455878600 −4.484154484 −1.00000000 51.982 44−226.630329417AS −24.123224774 CAF2HL −1.55840983 44.183 45897.778633917 −0.971829936 −1.00000000 33.797 46 0.000000000−9.700651756 CAF2HL −1.55840983 31.743 47 0.000000000 −7.828847134−1.00000000 26.288 48 0.000000000 0.000446630 −1.00000000 17.067ASPHERIC CONSTANTS SURFACE NO. 6 K 0.0000 C1 3.87858881e−009 C2−1.57703627e−013 C3 1.62703226e−017 C4 −1.12332671e−021 C5−1.51356191e−026 C6 8.57130323e−031 SURFACE NO. 12 K 0.0000 C13.87858881e−009 C2 −1.57703627e−013 C3 1.62703226e−017 C4−1.12332671e−021 C5 −1.51356191e−026 C6 8.57130323e−031 SURFACE NO. 19 K0.0000 C1 3.62918557e−009 C2 6.75596543e−014 C3 5.68408321e−019 C4−6.78832654e−023 C5 6.78338885e−027 C6 −2.05303753e−031 SURFACE NO. 21 K0.0000 C1 1.19759751e−008 C2 7.35438590e−014 C3 7.03292772e−019 C4−1.26321026e−023 C5 −3.01047364e−027 C6 2.08735313e−031 SURFACE NO. 28 K0.0000 C1 −8.39294529e−009 C2 −3.39607506e−013 C3 8.76320979e−018 C4−1.43578199e−021 C5 5.59234999e−026 C6 2.01810948e−030 SURFACE NO. 29 K0.0000 C1 1.74092829e−008 C2 −1.69607632e−013 C3 1.18281063e−017 C4−3.08190938e−021 C5 1.70082968e−025 C6 −1.68479126e−030 SURFACE NO. 34 K0.0000 C1 −2.14453018e−008 C2 6.73947641e−013 C3 −4.84677574e−017 C45.99264335e−021 C5 −2.87629386e−025 C6 3.90592520e−031 SURFACE NO. 38 K0.0000 C1 1.60415031e−008 C2 4.78837509e−015 C3 2.08320399e−016 C4−2.87713700e−020 C5 1.77485272e−024 C6 −1.93501550e−029 SURFACE NO. 44 K0.0000 C1 −6.56394686e−008 C2 −8.25210588e−012 C3 −1.27328625e−016 C4−1.16616292e−020 C5 −1.58133131e−023 C6 6.39526832e−027

TABLE 5 j33o REFRACTIVE INDEX ½ FREE SURFACE RADII THICKNESSES LENSES157.63 nm DIAMETER  0 0.000000000 38.054423655 1.00000000 85.333  1304.292982078 22.168809366 CAF2HL 1.55840983 92.441  2 2741.79448105096.128678854 1.00000000 92.171  3 0.000000000 0.000000000 −1.00000000131.865 REFL  4 0.000000000 −467.749539716 −1.00000000 90.082  5199.893955036 −10.268444544 CAF2HL −1.55840983 91.444  6 486.702942680AS−25.540971142 −1.00000000 96.627  7 186.738998389 −10.064297945 CAF2HL−1.55840983 98.903  8 447.975139348 −19.398954786 −1.00000000 110.873  9243.529966034 19.398954786 1.00000000 114.137 REFL 10 447.97513934810.064297945 CAF2HL 1.55840983 111.985 11 186.738998389 25.5409711421.00000000 102.576 12 486.702942680AS 10.268444544 CAF2HL 1.55840983101.403 13 199.893955036 465.154328539 1.00000000 96.394 14 0.0000000000.000000000 −1.00000000 115.447 REFL 15 0.000000000 −100.235657635−1.00000000 92.750 16 −536.44298965 −25.379215206 CAF2HL −1.5584098394.346 17 629.049380815 −8.324209221 −1.00000000 93.829 18 0.000000000−117.663111488 −1.00000000 91.238 19 −312.177007433AS −24.720749191CAF2HL −1.55840983 94.838 20 −734.696609024 −220.431435837 −1.0000000094.085 21 −277.004238298AS −15.426909916 CAF2HL −1.55840983 96.283 22−460.130899964 −74.271177440 −1.00000000 95.326 23 −158.318468619−30.586960517 CAF2HL −1.55840983 91.580 24 −162.867000225 −41.410948173−1.00000000 84.915 25 419.508310212 −20.539965049 CAF2HL −1.5584098384.171 26 −238.581080262 −32.165915708 −1.00000000 85.183 27−430.197019246 −30.182066783 CAF2HL −1.55840983 92.511 28691.939037816AS −23.123455275 −1.00000000 93.802 29 −241.462660758AS−10.000000000 CAF2HL −1.55840983 97.962 30 −182.472613831 −25.738903727−1.00000000 96.437 31 −420.041190250 −36.705938298 CAF2HL −1.5584098398.835 32 324.867666879AS −7.314163393 −1.00000000 99.389 33−149.830817441 −28.311419778 CAF2HL −1.55840983 94.515 34−315.631878253AS −15.768661491 −1.00000000 91.448 35 0.000000000−3.044279163 −1.00000000 91.163 36 −172.862510793 −12.271843841 CAF2HL−1.55840983 87.933 37 −115.635345524 −27.331297691 −1.00000000 81.792 38−229.213645994AS −32.436472831 CAF2HL −1.55840983 82.538 39474.721571790 −4.085179748 −1.00000000 81.887 40 −152.435372054−30.802088433 CAF2HL −1.55840983 75.743 41 −530.778945822 −8.090865960−1.00000000 70.786 42 −159.504999222 −41.060952888 CAF2HL −1.5584098363.559 43 3040.455878600 −4.476231798 −1.00000000 51.715 44−226.630329417AS −24.123224774 CAF2HL −1.55840983 44.004 45897.778633917 −0.971829936 −1.00000000 33.650 46 0.000000000−9.798128149 CAF2HL −1.55840983 31.626 47 0.000000000 0.000000000 IMMERS−1.39000000 26.153 48 0.000000000 −7.818040520 −1.00000000 26.153 490.000000000 0.000266950 −1.00000000 17.067 ASPHERIC CONSTANTS SURFACENO. 6 K 0.0000 C1 3.87858881e−009 C2 −1.57703627e−013 C3 1.62703226e−017C4 −1.12332671e−021 C5 −1.51356191e−026 C6 8.57130323e−031 SURFACE NO.12 K 0.0000 C1 3.87858881e−009 C2 −1.57703627e−013 C3 1.62703226e−017 C4−1.12332671e−021 C5 −1.51356191e−026 C6 8.57130323e−031 SURFACE NO. 19 K0.0000 C1 3.62918557e−009 C2 6.75596543e−014 C3 5.68408321e−019 C4−6.78832654e−023 C5 6.78338885e−027 C6 −2.05303753e−031 SURFACE NO. 21 K0.0000 C1 1.19759751e−008 C2 7.35438590e−014 C3 7.03292772e−019 C4−1.26321026e−023 C5 −3.01047364e−027 C6 2.08735313e−031 SURFACE NO. 28 K0.0000 C1 −8.39294529e−009 C2 −3.39607506e−013 C3 8.76320979e−018 C4−1.43578199e−021 C5 5.59234999e−026 C6 2.01810948e−030 SURFACE NO. 29 K0.0000 C1 1.74092829e−008 C2 −1.69607632e−013 C3 1.18281063e−017 C4−3.08190938e−021 C5 1.70082968e−025 C6 −1.68479126e−030 SURFACE NO. 32 K0.0000 C1 −3.60582630e−011 C2 2.95599027e−015 C3 −7.37891981e−019 C46.32721261e−023 C5 −3.13935388e−027 C6 0.00000000e+000 SURFACE NO. 34 K0.0000 C1 −2.14453018e−008 C2 6.73947641e−013 C3 −4.84677574e−017 C45.99264335e−021 C5 −2.87629386e−025 C6 3.90592520e−031 SURFACE NO. 38 K0.0000 C1 1.60415031e−008 C2 4.78837509e−015 C3 2.08320399e−016 C4−2.87713700e−020 C5 1.77485272e−024 C6 −1.93501550e−029 SURFACE NO. 44 K0.0000 C1 −6.56394686e−008 C2 −8.25210588e−012 C3 −1.27328625e−016 C4−1.16616292e−020 C5 −1.58133131e−023 C6 6.39526832e−027

1. A system, comprising: a projection objective configured to imageradiation from an object plane to an image plane, the projectionobjective having an optical axis, the projection objective comprising: aplurality of optical elements along the optical axis, the plurality ofoptical elements comprising a group of optical elements and a lastoptical element which is closest to the image plane; and a positioningdevice configured to move the last optical element relative to the imageplane, wherein the projection objective is configured to be used in amicrolithography projection exposure machine. 2.-39. (canceled)